For data storage systems that utilize tape, tape heads are utilized to perform read and/or write operations upon the tape while the tape is conveyed across the tape head. A profile of the tape head in a direction of tape motion is commonly referred to as a contour. The contour is designed to maintain the moving tape in contact with a surface of the tape head, especially in a region adjacent to devices that perform the read and/or write functions. The contact of the moving tape to the surface of the tape head is to be achieved while minimizing friction between the tape head and tape to minimize wear of the tape and the tape head.
Some prior art tape heads use a cylindrical tape head surface with transverse slots across an entire width of the tape head. In the absence of the transverse slots, air is introduced between the tape and the tape head, thereby disrupting contact between the tape and the tape head. With the transverse slots, the moving tape stays in contact with the tape head downstream of the transverse slot, thus creating friction across the entire width of the tape. A wrap angle is an angle at which the tape extends from the tape head relative to a longitudinal direction of travel, wherein the tape extends from the support surface at a location that is spaced inboard from an edge of the tape head. These contours operate at large nominal wrap angles and can tolerate a large variation in wrap angle.
In other prior art tape heads, flat support surfaces with reduced lengths are used to reduce the active area of contact and thus reduce friction upon the tape and the tape head as compared to the cylindrical contours. The tape is overwrapped at the corners of the flat surfaces that are perpendicular to the longitudinal direction. The overwrap scrapes off entrained air, thus creating contact between tape and the tape head, but creates contact pressure, which consequently causes friction. An overwrap angle is an angle at which the tape extends from an edge of the tape head relative to a support surface of the tape head. In this case, the overwrap angle is the same as the wrap angle defined earlier. Higher overwrap angles create higher contact pressure and friction. So, these contours typically operate at a lower nominal wrap angle and the wrap angle variation is more precisely controlled, especially to reduce wear of the tape as larger wrap angles can lead to higher tape wear. The wrap angle (and overwrap angle) is dictated by the location of the head in the tape path of the tape drive, or more precisely, by the location of the tape path guides adjacent to the head. Typically, the head is manufactured separately and then integrated into the tape path during drive manufacturing, leading to larger variations in the wrap angles presented to the contour. In addition, heads with newer overwrapped contour designs can be installed in tape drives with tape paths designed with larger nominal wrap angles of the earlier transverse slotted cylindrical contour designs.
For these overwrapped contours, it is desired to present a low nominal wrap angle with tight tolerances to the active head contour, irrespective of the nominal wrap angle and tolerances dictated by the tape path. One current solution includes installation of additional inactive cylindrical modules (known as outriggers) onto either side of the active modules (read/write heads) such that the entire assembly (outriggers and overwrapped modules) works for any reasonable nominal wrap angle or variation from the tape path. The outriggers are designed so that there is negligible friction between the tape and the outriggers at the operational tape speed. The outriggers are assembled to the active modules such that the overwrap on the active modules is minimized to reduce friction. This approach leads to additional processes to fabricate and assemble the outriggers; and increases the physical size of the tape head assembly, which may interfere with other components in the tape drive. This issue is amplified when the size of the active tape head assembly increases due to architectural changes, such as an increase in the number of active modules used.
Another solution is to introduce mechanisms in the tape path to precisely control the wrap angle during the integration of the head assembly into the tape path during drive manufacturing. This greatly increases the process complexity for integrating the head assembly into the drive.